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| United States Patent |
5,229,687
|
|
Fowler
, et al.
|
July 20, 1993
|
Mercury vapor discharge lamp containing means for reducing mercury
leaching
Abstract
A mercury vapor discharge lamp having an envelope of light-transmitting
vitreous material containing an inert starting gas and a quantity of
elemental mercury at least partially convertible to soluble mercury.
Enclosed within the lamp is an amount of chemical agent suitable for
electrochemically reducing a substantial portion of the soluble mercury to
elemental mercury when the lamp is pulverized as a result of disposal.
Preferably, the chemical agent is an element (i.e., copper or iron) which
has an electrode potential for oxidation reactions higher than mercury. In
a preferred embodiment, the chemical agent is sealed within an enclosure
(e.g., glass) which is rupturable upon pulverization of the lamp. The
sealed enclosure is disposed within the envelope or external to the
envelope, such as within a cavity defined by a lamp base member. In
another embodiment, the chemical agent is mixed with the basing cement
used to secure the lamp bases to the envelope.
| Inventors:
|
Fowler; Richard A. (Ipswich, MA);
Bonazoli; Robert P. (Hamilton, MA)
|
| Assignee:
|
GTE Products Corporation (Danvers, MA)
|
| Appl. No.:
|
773835 |
| Filed:
|
October 9, 1991 |
| Current U.S. Class: |
313/565; 313/318.01; 313/318.02; 313/485; 313/490; 445/2; 445/61; 445/73 |
| Intern'l Class: |
H01J 061/00 |
| Field of Search: |
313/493,565,490,485,318,546,549
445/2,61,73
|
References Cited
U.S. Patent Documents
| 3392298 | Jul., 1968 | Menelly | 313/109.
|
| 4047071 | Sep., 1977 | Busch et al. | 313/490.
|
| 4105910 | Aug., 1978 | Evans | 313/490.
|
| 4145634 | Mar., 1979 | Evans et al. | 313/490.
|
| 4268306 | May., 1981 | Bjorkman | 75/81.
|
| 4380714 | Apr., 1983 | Bouman et al. | 313/549.
|
| 4435284 | Mar., 1984 | Heytmeijer | 209/3.
|
| 4481442 | Nov., 1984 | Albrecht et al. | 313/493.
|
| 4715838 | Dec., 1987 | Kulander | 445/61.
|
| 4907998 | Mar., 1990 | Kuijer et al. | 313/490.
|
| Foreign Patent Documents |
| 58-184558 | Oct., 1983 | JP.
| |
Other References
Federal Register, pp. 26987-26998, vol. 55, No. 126, Jun. 29, 1990.
Experimental Electrochemistry For Chemists, pp. 303-304, 1974.
The Condensed Chemical Dictionary, p. 434, 1961.
Glossary of Chemical Terms, p. 6, 1982.
|
Primary Examiner: Yosko; Donald J.
Assistant Examiner: Patel; N. D.
Attorney, Agent or Firm: Bessone; Carlo S.
Claims
What is claimed is:
1. In a mercury vapor discharge lamp having an envelope of
light-transmitting vitreous material containing an inert starting gas and
a quantity of elemental mercury at least partially convertible to soluble
mercury, first and second electrodes located within said envelope for
establishing an arc discharge therebetween, the improvement comprising: an
effective amount of a chemical agent located within said lamp so as not to
interfere with the arc discharge or the operation of the lamp, said
chemical agent electrochemically reducing portion of said soluble mercury
to elemental mercury when said lamp is pulverized to granules and
subjected to a suitable aqueous acid solution, said chemical agent being
in an amount such that the remaining portion of soluble mercury leachable
after said portion of soluble mercury is electrochemically reduced to
elemental mercury is less than 0.2 milligram per liter of said aqueous
acid solution.
2. The mercury vapor discharge lamp of claim 1 wherein said chemical agent
is an element having an electrode potential for oxidation reactions higher
than mercury but not sufficiently active to displace hydrogen from said
aqueous acid solution.
3. The mercury vapor discharge lamp of claim 2 wherein said chemical agent
is selected from the group consisting of iron, copper, tin, indium,
nickel, cobalt and titanium.
4. The mercury vapor discharge lamp of claim 3 wherein said chemical agent
comprises approximately 0.5 to 5 grams of copper powder or copper dust.
5. The mercury vapor discharge lamp of claim 3 wherein said chemical agent
comprises approximately 0.25 gram to 5 grams of iron powder.
6. The mercury vapor discharge lamp of claim 1 wherein said chemical agent
is contained within a sealed enclosure, said sealed enclosure being
rupturable upon pulverization of said lamp.
7. The mercury vapor discharge lamp of claim 6 wherein said sealed
enclosure is disposed within said envelope.
8. The mercury vapor discharge lamp of claim 6 further comprising at least
one base member secured to said envelope and defining a cavity, said
sealed enclosure containing said chemical agent being disposed within said
cavity of said base member.
9. The mercury vapor discharge lamp of claim 6 wherein said sealed
enclosure containing said chemical agent is glass.
10. The mercury vapor discharge lamp of claim 1 wherein said lamp comprises
at least one base member secured to said envelope with basing cement
means, said chemical agent being mixed with said basing cement means.
11. In a mercury vapor discharge lamp having an envelope of
light-transmitting vitreous material containing an inert starting gas and
a quantity of elemental mercury at least partially convertible to soluble
mercury, first and second electrodes located within said envelope for
establishing an arc discharge therebetween, the improvement comprising: an
effective amount of a chemical agent selected from the group consisting of
iron, copper, tin, nickel, cobalt and titanium located within said lamp,
said chemical agent electrochemically reducing a portion of said soluble
mercury to elemental mercury when said lamp is pulverized to granules and
subjected to a suitable aqueous acid solution, said chemical agent being
in an amount such that the remaining portion of soluble mercury leachable
after said portion of soluble mercury is electrochemically reduced to
elemental mercury is less than 0.2 milligram per liter of said aqueous
acid solution.
12. The mercury vapor discharge lamp of claim 11 wherein said chemical
agent is disposed within said envelope.
13. The mercury vapor discharge lamp of claim 11 further comprising at
least one base member secured to said envelope and defining a cavity, said
chemical agent being disposed within said said cavity.
14. The mercury vapor discharge lamp of claim 11 wherein said lamp
comprises at least one base member secured to said envelope with basing
cement means, said chemical agent being mixed with said basing cement
means.
15. The mercury vapor discharge lamp of claim 11 wherein said lamp is a
fluorescent lamp.
Description
CROSS-REFERENCE TO A RELATED APPLICATION
This application discloses, but does not claim, inventions which are
claimed in U.S. Ser. No. 07/773,834 filed concurrently herewith and
assigned to the Assignee of this application.
FIELD OF THE INVENTION
This invention relates in general to mercury vapor arc discharge lamps and
pertains, more particularly, to a fluorescent lamp which contains a
chemical agent for substantially reducing the amount of soluble mercury
measurable after pulverization of the lamp.
BACKGROUND OF THE INVENTION
Fluorescent lamps are well known in the art and are characterized as low
pressure arc discharge lamps which include a pair of electrodes sealed in
an elongated envelope whose interior surface is coated with phosphor. The
envelope contains a quantity of mercury and a rare gas at a reduced
pressure, for example, in the order of 1-5 torr.
During lamp manufacture, about 10-40 milligrams of elemental mercury is
sealed in each fluorescent lamp. It is known that most of this mercury
adheres to the phosphor coating with only a very small portion of the
mercury being in the form of mercury vapor. After the alkali earth metal
oxides coating the lamp electrodes are volatized, the oxides decompose in
the discharge space and the freed oxygen converts some of this elemental
mercury to a salt or compound such as mercuric oxide (HgO) which is highly
soluble.
There is a growing concern that a waste stream resulting from the disposal
of fluorescent lamps may leach excessive amounts of this soluble form of
mercury. One method of measuring the amount of soluble mercury which may
leach from the waste stream resulting from the disposal of fluorescent
lamps is described in the Toxicity Characteristic Leaching Procedure
(TCLP) prescribed on pages 26987-26998 of volume 55, number 126 of the
Jun. 29, 1990 issue of the Federal Register. According to the procedure,
the lamp being tested is pulverized into granules having a surface area
per gram of material equal to or greater than 3.1 cm.sup.2 or having a
particle size smaller than 1 cm in its narrowest dimension. Following
pulverization, the granules are subjected to a sodium acetate buffer
solution having a pH of approximately 4.93 and having a weight twenty
times the weight of the granules.
At the present time, the Environmental Protection Agency defines a maximum
concentration level for mercury at 0.2 milligram leachable mercury per
liter extract fluid when the TCLP is applied. According to present
standards, a fluorescent lamp is considered non leachable when less than
0.2 milligram per liter of leachable mercury results from a TCLP
extraction.
Various methods have been proposed which attempt to treat or process
burned-out discharge lamps or scrap lamp exhaust tubing containing mercury
in order to reclaim the mercury and thereby reduce the amount of
mercury-contaminated scrap glass. For example, U.S. Pat. No. 4,268,306
(Bjorkman) discloses a treatment whereby the expanded or scrapped lamps
are crushed into fragments which are then placed in a treatment vessel in
which the mercury is recovered by distillation processes. This treatment
is carried out batchwise in a sealed container into which nitrogen is
introduced. The container is heated and placed under vacuum so as to
vaporize the mercury. The vaporized mercury is then removed from the
container through a bottom outlet and condensed in a cooling trap. It is
apparent that following the process, the treated lamp fragments (i.e.,
glass and phosphor) may be dumped without concerns about mercury leaching.
U.S. Pat. No. 4,715,838 (Kulander) teaches a method and apparatus for
recovering the luminescent material from mercury vapor electric discharge
lamps whereby the amount of lamp waste requiring treatment in the
distillation chamber can be reduced thereby increasing the capacity of the
chamber with respect to the number of lamps. After the ends of the lamp
bulb or tube are separated from the intermediate bulb, the luminescent
material is loosened from the inner wall surface of the bulb part with the
aid of a stripping device which is arranged to be inserted into the bulb
part from one end thereof. The loosened material is collected with the aid
of a suction device connected to the other end of the bulb part and
thereafter may be introduced into the distillation chamber, thereby
obviating the need to fill the chamber with the residual "clean" glass
bulb.
Japanese Patent Application No. 58-184558 (Kitsugi et. al.) teaches a
method for solidifying discarded fluorescent lamps and insolubilizing the
mercury contained therein. The method involves adding sulfur to crushed
fluorescent lamp waste in the proportion of 0.1-5 parts by weight per 100
parts by weight of the discard. The result is placed into a ball mill and
pulverized an amount of time sufficient to produce granules with sizes 5
millimeters or less. Cement and water were added and the result is
kneaded. The kneaded material prepared in this way is put into molds so as
to form a stabilized solidified material having a mercury concentration of
less than 0.005 milligram per liter water.
U.S. Pat. No. 4,435,284 (Heytmeijer) teaches a process for removing
residual mercury from scrap fluorescent lamp exhaust tubulation or similar
scrap glass. A very small predetermined amount of finely divided silica or
alumina powder is added to the mercury contaminated scrap glass and the
mixture is agitated for a very short predetermined time during which the
mercury is stripped from the tubulation. The separated mercury, powder and
glass mixture is then decanted through a screen of suitable mesh to remove
the separated mercury and powder from the glass and the mercury is then
rinsed with a suitable solvent to remove the oxide powder from the
mercury.
While these processes may be effective in separating mercury from lamp
fragments or scrap glass or for insolubilizing the mercury contained in
discarded fluorescent lamps, each process requires treatment equipment
which may be relatively expensive.
SUMMARY OF THE INVENTION
It is, therefore, an object of the present invention to obviate the
disadvantages of the prior art.
It is still another object of the invention to provide a mercury vapor
discharge lamp which can be considered non leaching upon disposal.
It is another object of the invention to provide a mercury vapor discharge
lamp which can be disposed of without prior expensive treatment to reclaim
mercury.
These objects are accomplished in one aspect of the invention by the
provision of a mercury vapor discharge lamp having an envelope of
light-transmitting vitreous material containing an inert starting gas and
a quantity of elemental mercury at least partially convertible to soluble
mercury. First and second electrodes are located within the envelope for
establishing an arc discharge therebetween. An effective amount of a
chemical agent suitable for electrochemically reducing a substantial
portion of the soluble mercury to elemental mercury when the lamp is
pulverized to granules and subjected to a suitable aqueous acid solution
is located within the lamp and effectively remote from the arc discharge.
In accordance with further teachings of the present invention, the chemical
agent is an element having an electrode potential for oxidation reactions
higher than mercury but not sufficiently active to displace hydrogen from
the aqueous acid solution. Preferably, the chemical agent is selected from
the group consisting of iron, copper, tin, indium, nickel, cobalt and
titanium. In one embodiment, the chemical agent comprises approximately
0.5 to 5 grams of copper powder or copper dust. In another embodiment, the
chemical agent comprises approximately 0.25 gram to 5 grams of iron
powder.
In accordance with further aspects of the present invention, the lamp
further includes a sealed enclosure (e.g., glass) for containing the
chemical agent. The sealed enclosure is disposed within the envelope or
external to the envelope, such as with a cavity defined by a lamp base
member. The sealed enclosure is rupturable upon pulverization of the lamp.
In accordance with still further aspects of the present invention, the
chemical agent is mixed with the basing cement used to secure one or more
of the lamp bases to the lamp envelope.
Additional objects, advantages and novel features of the invention will be
set forth in the description which follows, and in part will become
apparent to those skilled in the art upon examination of the following or
may be learned by practice of the invention. The aforementioned objects
and advantages of the invention may be realized and attained by means of
the instrumentalities and combination particularly pointed out in the
appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will become more readily apparent from the following
exemplary description in connection with the accompanying drawings,
wherein:
FIG. 1 represents a front elevational view, partially broken away, of a
mercury vapor discharge lamp according to the present invention;
FIG. 2 is a perspective view of a portion of a mercury vapor discharge lamp
according to one embodiment of the invention; and
FIG. 3 is a perspective view of a portion of a mercury vapor discharge lamp
according to another embodiment of the invention.
BEST MODE FOR CARRYING OUT THE INVENTION
For a better understanding of the present invention, together with other
and further objects, advantages and capabilities thereof, reference is
made to the following disclosure and appended claims in connection with
the above-described drawings.
To overcome the disadvantages mentioned above with respect to the prior
art, the present invention provides a method of rendering the mercury in a
mercury vapor discharge lamp non leachable upon disposal without
necessitating the need for relatively expensive treatment equipment as
discussed above. More specifically, the invention prevents leaching of
mercury as measured by TCLP by the incorporation of a substance (i.e.,
materials or agents) in the lamp construction which renders the mercury
non leachable upon disposal. In accordance with the teachings of the
present invention, these substances comprise chemical agents (i.e.,
elements, compounds or combinations thereof) which electrochemically have
the potential to reduce soluble mercury produced during lamp operation to
elemental mercury. Elemental (metallic) mercury is not leachable as
measured by the TCLP.
In one embodiment, the chemical agent is located "effectively remote" from
the arc discharge so as not to interfere with the discharge or the
operation of the lamp. One suitable method for disposing the chemical
agent "effectively remote" from the discharge is to contain the chemical
agent within a sealed enclosure within the lamp envelope. Alternatively,
the chemical agent may be disposed remote from the arc discharge by
disposing the chemical agent within one or more of the lamp bases. In the
latter instance, the chemical agent may be located within a cavity formed
by the lamp base or may be mixed with the basing cement used to secure the
lamp base(s) to the envelope. If the chemical agent is placed within the
base cavity, the chemical agent may be further contained within a sealed
enclosure secured to an inner surface of the base.
Referring to the drawings with greater particularity, there is illustrated
in FIG. 1 a mercury vapor discharge lamp 10, such as a fluorescent lamp,
comprising an elongated sealed envelope 12 of light-transmitting vitreous
material. Envelope 12 is filled with an inert gas such as argon at a low
pressure, for example two torr, and a quantity of mercury 40, at least
enough to provide a low vapor pressure of about six mm. of Ag during
operation. An electrode 14 and 16 is disposed at each end of envelope 12
supported by lead-in wires 18, 20, and 22, 24, respectively. Electrodes 14
and 16 are coated with electron-emitting materials such as BaO--SrO--CaO
containing MgZrO.sub.3. The lead-in wires extend through stem presses 26,
28 in mount stems 30, 32 to the contacts in base members 34, 36 secured to
the ends of envelope 12.
A phosphor coating 38 is disposed on the interior surface of envelope 12.
Phosphor coating 38, which may be a halophosphate phosphor such as Cool
White, is responsive to the ultraviolet radiation generated by the arc
discharge established between electrodes 14, 16 to provide a desired
emission spectrum.
During lamp manufacture, about 10-40 milligrams of elemental mercury is
sealed in each fluorescent lamp. During lamp life, most of this mercury
adheres to the phosphor coating with only a very small portion of the
mercury being in the form of mercury vapor. After the alkali earth metal
oxides coating the lamp electrodes are volatized, the oxides decompose in
the discharge space and the freed oxygen converts some of this elemental
mercury to a salt or compound such as mercuric oxide (HgO) which is highly
soluble.
In accordance with the teaching of the present invention, located within
the lamp is an effective . amount of a chemical agent 42 suitable for
electrochemically reducing a substantial portion of the soluble mercury
available within the lamp to elemental mercury measurable when the lamp is
pulverized to granules and subjected to a suitable aqueous acid solution.
Evidence of a substantial portion of the soluble mercury having been
reduced is apparent when the amount of soluble mercury is less than 0.2
milligram per liter of the aqueous acid solution.
Soluble mercury is produced during lamp operation and during TCLP as the
result of the action of elemental mercury with other metals found in the
lamp (e.g., lead wires and metal bases). The chemical agent is generally
an element, compound or combinations thereof which is described as "more
active" or "higher" than mercury in a listing of the standard electrode
potentials for oxidation reactions in the Electrochemical (or
Electromotive) Series of Oxidation Potentials. Typically, the chemical
agent should be more active than mercury in order to displace mercury ions
but not sufficiently active to displace hydrogen from water or a mild
acid. Preferably, the chemical agent is selected from the group consisting
of iron, copper, tin, indium, nickel, cobalt and titanium.
The chemical agent may be used in various forms. For example, the chemical
agent may be in the form of a powder, dust, wire mesh or metallic foil.
The amount or size of the chemical agent is directly related to the
surface area and surface condition. A metallic powder or dust is preferred
over a solid mass because of their large effective surface areas. Because
of their availability and inexpensive cost, iron and copper, in the form
of a powder or dust, are preferred. Typical amounts of iron and copper
which are effective in reducing the amount of leachable mercury are from
about 0.1 gram to 10 grams.
Preferably, the amount of chemical agent present is sufficient to
electrochemically reduce the amount of soluble mercury within the lamp
which is leached at the time of disposal to less than 0.2 milligram per
liter of an aqueous acid solution such as a sodium acetate buffer solution
as prescribed by TCLP. An effective amount of iron powder is at least
about 0.25 gram.
Referring next to FIGS. 2 and 3, there are shown two preferred embodiments
of the present invention, wherein several of the same constituent members
as those in FIG. 1 are denoted by the same reference numerals In the first
embodiment as illustrated in FIG. 2, chemical agent 42 is contained in a
sealed enclosure or vial 44 disposed within lamp envelope 12. The sealed
enclosure is formed from a material which is easily rupturable when the
lamp is crushed for disposal in a landfill or to meet the size reduction
required by TCLP. Rupture of the sealed enclosure facilitates dispersion
of the chemical agent with the lamp granules. Glass is a suitable material
for sealed enclosure 44.
In order to prevent movement of the sealed enclosure within the lamp
envelope, sealed enclosure 44 containing chemical agent 42 may be secured
to mount stem 30 by a suitable means. In FIG. 2, a securing wire or strap
46 is wrapped around mount stem 30 and sealed enclosure 44.
In the second embodiment as illustrated in FIG. 3, sealed enclosure 44
containing chemical agent 42 is disposed external to envelope 12 and
within a cavity 48 formed by base member 34. To prevent movement within
the base member, the sealed enclosure may be secured to an inner surface
of the base member by a suitable means such as an epoxy or cement (not
shown).
Sealing the chemical agent within the enclosure 44 facilitates handling of
the material during manufacturing and insures that the active material
remains contained during normal lamp life. Moreover, in the embodiment
illustrated in FIG. 2, the sealed enclosure prevents the active material
from adversely affecting the arc discharge or the phosphor coating during
lamp operation.
Indium has been used in mercury discharge lamps in the past as an
amalgam-forming material for regulating the mercury vapor pressure and
thus permitting the lamp to be operated at high power loadings and under
high ambient temperature conditions. Typically, the amount of indium in
such an application may be in the order of 150 milligrams. Since in the
present invention it is desirable that the chemical agent not affect the
mercury vapor pressure, the indium (or any other chemical agent which may
otherwise affect the operation of the lamp) is preferably disposed
external to the lamp envelope (e.g., in the lamp base) or, if disposed
within the lamp envelope, should remain contained within a sealed
enclosure during lamp operation.
It is within the scope of the invention to dispose the chemical agent in
locations other than those shown in the drawings. For example, it is
possible to locate the sealed enclosure containing the chemical agent at a
location 50 (FIG. 3) within mount stem 30. Alternatively, the chemical
agent may include an alloy from which the base member is made of a coating
of the chemical agent on a surface of at least one of the lamp base
members 34, 36. The chemical agent may also be incorporated with the
adhesive or basing cement 52 (FIG. 3) used to secure one or more of the
base members 34, 36 to lamp envelope 12. Finally, the chemical agent may
be disposed at more than one location within the lamp.
EXAMPLE I--COPPER
In a typical but non-limitative example of a mercury vapor discharge lamp
in accordance with the teachings of the present invention, both "new" and
"used" 40-watt Cool White fluorescent lamps in the presence of 5 grams of
either copper metal powder or or copper metal dust are subjected to the
Federal TCLP for leachable mercury. The "used" lamps utilized in the test
were lamps expected to be near the end of life.
In one test, copper metal powder available from Fisher Scientific and
designated #C434 is first subjected to a dilute HCl wash prior to use.
This material has a surface area of 0.34 meter.sup.2 /gram. In the other
test, copper metal dust also available from Fisher Scientific and
designated #431 is utilized without prewashing. This latter material has a
surface area of 0.35 meter.sup.2 /gram. According to the TCLP measuring
procedure, each lamp is pulverized into granules having a surface area per
gram of material equal to or greater than 3.1 cm.sup.2 or having a
particle size smaller than 1 cm in its narrowest dimension. Following
pulverization, the granules are subjected to a sodium acetate buffer
solution having a pH of approximately 4.93 and having a weight twenty
times the weight of the granules. Mercury in the TCLP extract is
determined by cold vapor atomic absorption spectrometry as prescribed by
the TCLP procedure. The results of these tests are shown in the following
TABLE I:
TABLE I
______________________________________
ACTIVE AMOUNT OF MERCURY
LAMP SUBSTANCE LEACHED BY TCLP
______________________________________
F40/CW 5 GRAMS 0.06 MG/L
(NEW) COPPER POWDER
F40/CW 5 GRAMS 0.14 MG/L
(USED) COPPER POWDER
F40/CW 5 GRAMS 0.12 MG/L
(NEW) COPPER DUST
F40/CW 5 GRAMS 0.18 MG/L
(USED) COPPER DUST
______________________________________
Typical TCLP results obtained on similar lamps but not containing an
effective amount of a chemical agent as described by the present invention
range from 0.3 mg/L Hg to 2.3 mg/L Hg. According to TABLE I, it is evident
that the addition of 5 grams of copper powder or copper dust substantially
reduces the amount of soluble mercury.
EXAMPLE II--COPPER
In a second example of a mercury vapor discharge lamp in accordance with
the teachings of the present invention, 20-watt Cool White fluorescent
lamps in the presence of approximately 5 grams of either copper metal
dust, a mesh of copper, or a sheet of copper are subjected to the Federal
TCLP for leachable mercury. The copper metal dust is similar to that used
in the previous test. The copper mesh is constructed from strands having a
0.15 millimeter diameter. The copper sheet consists of 35 pieces of copper
each measuring 5.5 millimeters by 50 millimeters.
According to the TCLP measuring procedure, each lamp is pulverized into
granules having a surface area per gram of material equal to or greater
than 3.1 cm.sup.2 or having a particle size smaller than 1 cm in its
narrowest dimension. Following pulverization, the granules are subjected
to a sodium acetate buffer solution having a pH of approximately 4.93 and
having a weight twenty times the weight of the granules. Mercury in the
TCLP extract is determined by cold vapor atomic absorption spectrometry as
prescribed by the TCLP procedure. The results of these tests are shown in
the following TABLE II:
TABLE II
______________________________________
SURFACE
ACTIVE AREA AMOUNT OF MERCURY
SUBSTANCE OF COPPER LEACHED BY TCLP
______________________________________
NO COPPER -- 0.63 MG/L
ADDITION
COPPER DUST 1.8 SQ. 0.05 MG/L
(5 GRAMS) METER
COPPER MESH 0.03 SQ. 0.11 MG/L
(4.9 GRAMS) METER
COPPER SHEET
0.01 SQ. 0.19 MG/L
(5 GRAMS) METER
______________________________________
TABLE II above shows the effect of various forms of copper and their
resulting surface areas on the amount of mercury leached by TCLP. It is
apparent therefrom that in order to limit the amount of soluble mercury to
less than 0.2 milligram per liter of the aqueous acetate solution used in
the test procedure, the total surface area of the active substance should
be greater than or equal to approximately 0.01 meter.sup.2.
EXAMPLE III--IRON
In another example of a mercury vapor discharge lamp in accordance with the
teachings of the present invention, 40-watt Cool White fluorescent lamps
in the presence of 0.5 to 5 grams of iron powder are subjected to the
Federal TCLP for leachable mercury. Suitable iron powder is available from
Fisher Scientific and designated I60. The surface area of the powdered
iron is 0.15 meter.sup.2 /gram. According to the TCLP measuring procedure,
each lamp is pulverized into granules having a surface area per gram of
material equal to or greater than 3.1 cm.sup.2 or having a particle size
smaller than 1 cm in its narrowest dimension. Following pulverization, the
granules are subjected to a sodium acetate buffer solution having a pH of
approximately 4.93 and having a weight twenty times the weight of the
granules. Mercury in the TCLP extract is determined by cold vapor atomic
absorption spectrometry as prescribed by the TCLP procedure. The results
of these tests are shown in the following TABLE III:
TABLE III
______________________________________
SURFACE
ACTIVE AREA AMOUNT OF MERCURY
SUBSTANCE OF IRON LEACHED BY TCLP
______________________________________
NO IRON -- 0.63 MG/L
ADDITION
IRON POWDER 0.075 SQ. 0.11 MG/L
(0.5 GRAM) METER
IRON POWDER 0.15 SQ. 0.05 MG/L
(1 GRAM) METER
IRON POWDER 0.75 SQ. 0.05 MG/L
(5 GRAMS) METER
______________________________________
Table III would suggest that the quantity of iron powder necessary to limit
the amount of soluble mercury to less than 0.2 milligram per liter of the
aqueous acetate solution used in the test procedure, can be even less than
0.5 gram which translates into a surface area being less than 0.075
meter.sup.2.
EXAMPLE IV--IRON
In a fourth example of a mercury vapor discharge lamp in accordance with
the teachings of the present invention, 20-watt Cool White fluorescent
lamps in the presence of iron metal dust, iron wire, or iron foil are
subjected to the Federal TCLP for leachable mercury. The iron powder is
similar to that used in the previous test. The iron wire has a length of
1500 millimeters and a diameter of 0.23 millimeter and is of reagent
grade. The iron foil consists of three 0.127 millimeter thick pieces
having the following dimensions: 1.2 mm by 25 mm, 6.2 mm by 25 mm, and 9.6
mm by 25 mm. The iron foil is available from Strem Chemical and is
designated #93-2661. According to the TCLP measuring procedure, each lamp
is pulverized into granules having a surface area per gram of material
equal to or greater than 3.1 cm.sup.2 or having a particle size smaller
than 1 cm in its narrowest dimension. Following pulverization, the
granules are subjected to a sodium acetate buffer solution having a pH of
approximately 4.93 and having a weight twenty times the weight of the
granules. Mercury in the TCLP extract is determined by cold vapor atomic
absorption spectrometry as prescribed by the TCLP procedure. The results
of these tests are shown in the following TABLE IV:
TABLE IV
______________________________________
SURFACE
ACTIVE AREA AMOUNT OF MERCURY
SUBSTANCE OF IRON LEACHED BY TCLP
______________________________________
NO IRON -- 0.93 MG/L
ADDITION
IRON POWDER 0.015 SQ. 0.83 MG/L
(0.1 GRAM) METER
IRON POWDER 0.038 SQ. 0.19 MG/L
(0.25 GRAM) METER
IRON POWDER 0.15 SQ. LESS THAN
(1.0 GRAM) METER 0.05 MG/L
IRON WIRE 0.001 SQ. 0.35 MG/L
(0.5 GRAM) METER
IRON FOIL 0.0004 SQ.
0.65 MG/L
(0.5 GRAM) METER
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TABLE IV above shows the effect of surface area active material on the
amount of mercury leached by TCLP. It is apparent therefrom that in order
to limit the amount of soluble mercury to less than 0.2 milligram per
liter of the aqueous acid solution used in the test procedure, the weight
of the iron powder should be greater than or equal to 0.25 gram which
translates into a total surface area greater than or equal to
approximately 0.038 meter.sup.2. While the iron wire and iron foil reduced
the amount of soluble mercury leached by TCLP to 0.35 and 0.65 milligram
per liter, respectively, it is believed that increasing the surface area
of the wire or foil is necessary in order to limit the amount of soluble
mercury to less than 0.2 milligram per liter.
EXAMPLE V--IRON IN BASING CEMENT
In a fifth example of a mercury vapor discharge lamp in accordance with the
teachings of the present invention, each lamp base member was secured to
respective ends of a group of new 40-watt Cool White fluorescent lamps by
means of basing cement containing 0.5 gram of powdered iron. Suitable iron
powder is available from Fisher Scientific and designated I60. The surface
area of the powdered iron is 0.15 meter.sup.2 per gram. The basing cement
into which the iron powder was mixed is manufactured by GTE Product
Corporation in Towanda, PA. According to the TCLP measuring procedure,
each lamp is pulverized into granules having a surface area per gram of
material equal to or greater than 3.1 cm.sup.2 or having a particle size
smaller than 1 cm in its narrowest dimension. Following pulverization, the
granules are subjected to a sodium acetate buffer solution having a pH of
approximately 4.93 and having a weight twenty times the weight of the
granules. Mercury in the TCLP extract is determined by cold vapor atomic
absorption spectrometry as prescribed by the TCLP procedure. The results
of this test is shown in the following TABLE V:
TABLE V
______________________________________
SURFACE AMOUNT OF
ACTIVE AREA OF MERCURY LEACHED
SUBSTANCE IRON POWDER BY TCLP
______________________________________
NO IRON -- 0.56 MG/L
ADDITION
IRON POWDER
0.075 SQ. 0.09 MG/L
IN BASING METER
CEMENT
(0.5 .times. 2 GRAM)
______________________________________
TABLE V above shows that iron powder mixed in the basing cement of new
40-watt fluorescent lamps electrochemically reduces a substantial portion
of soluble mercury to elemental mercury when subjected to TCLP. Since the
amount of soluble mercury within a lamp increases as the lamp ages, it is
believed that in order to insure that a substantial portion of the soluble
mercury in an aged lamp is reduced to elemental mercury, approximately 1.0
gram of iron powder should be mixed with the basing cement of each base.
There has thus been shown and described a mercury vapor discharge lamp
containing a chemical agent for substantially reducing the amount of
soluble mercury measurable after pulverization of the lamp. The invention
provides a discharge lamp which can be disposed of in a landfill without
prior expensive treatment to reclaim mercury.
While there have been shown and described what are at present considered to
be the preferred embodiments of the invention, it will be apparent to
those skilled in the art that various changes and modifications can be
made herein without departing from the scope of the invention. Therefore,
the aim in the appended claims is to cover all such changes and
modifications as fall within the true spirit and scope of the invention.
The actual scope of the invention is intended to be defined in the
following claims when viewed in their proper perspective based on the
prior art.
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